1. Field of the Invention
The present invention relates to refrigerant compositions for use in refrigerating systems, and which have considerably reduced potential for ozone-depletion of the ozonosphere.
2. Description of the Prior Art
Conventionally, halogenated hydrocarbon refrigerants have been used as refrigerants for refrigerating systems. Among them, typically used are R-12 (dichlorodifluoromethane) and R-500 [an azeotropic mixture of R-12 and R-152a (1,1-difluoroethane)].
Under atmospheric pressure, the boiling points of R-12 and R-500 are -29.65.degree. C. and -33.45.degree. C., respectively, which are suitable for refrigerating systems. Further, even if their compressor inlet temperatures are comparatively high, their compressor outlet temperatures do not rise so high as to cause oil-sludge in the compressor. In addition, R-12 is highly compatible with an compressor oil, and hence plays a role of returning the entrained oil existing in a refrigerant circuit to the compressor.
However, the above refrigerants have high ozone-depletion potentials, and when released in the atmosphere and reached the ozonosphere, they destroy ozone of the ozonosphere. This destruction is caused by chlorine of refrigerant molecules.
To solve this problem, refrigerants excluding chlorine, for example, R-125 (pentafluoroethane, CHF.sub.2 CF.sub.3 ), R-134a (1,1,1,2-tetrafluoroethane, CH.sub.2 FCF.sub.3), and R-23 (trifluoromethane, CF.sub.3 H) are considered to be alternative refrigerants. Boiling points of R-125, R-134a and R-23 are -48.degree. C., -26.degree. C. and -82.05.degree. C., respectively under atmospheric pressure.
R-22 (monochlorodifluoromethane, CClF.sub.2 H) and R-142b (1-chloro-1,1-difluoroethane, C.sub.2 ClF.sub.2 H.sub.3) contain chlorine molecules therein. However, they rarely destroy ozone of the ozonosphere because of their decomposition before reaching there with the help of hydrogen (H) contained therein. Boiling points of R-22 and R-142b are -40.75.degree. C. and -9.8.degree. C., respectively under atmospheric pressure.
U.S. Pat. No. 4,810,403, for example, discloses some blends of the above refrigerants not adversely affecting the ozonosphere, each of which is a combination of two or more of the above refrigerants.
However, such blends of the refrigerants as disclosed in the above U.S. Pat. have the following disadvantages. The blends of R-125 R-134a, or R-23 are extremely poor in compatibility with compressor oils used in a refrigerating cycle because the compatibility with the oils depends mainly upon chlorine (Cl) of the refrigerants. As well, the blends of R-22 or R-142b, although they contain chlorine, do not exhibit satisfactory compatibility with naphthene or paraffin oils.
Where a refrigerant has poor compatibility with a compressor oil, separation into two phases (oil and refrigerant) occurs in an evaporator so that the oil scarcely returns to the compressor, with the result that bearing portions of the compressor may seize. In addition, the oil becomes liable to adhere to the piping of the refrigerating circuit, resulting in blockage of the refrigerating circuit.
The lower the boiling point of a blended refrigerant, the more conspicuous becomes this tendency. Especially, a serious problem exists in application of the blended refrigerants to a refrigerating system requiring a refrigerating temperature of lower than -20.degree. C., for example, -40.degree. C. or -80.degree. C.
Japanese Published Unexamined Patent Application Hei 1-141982 discloses a blended composition of R-134a and dichloromonofluoromethane (R-21) and teaches its application to refrigerating systems. However, where such a composition is used as a refrigerant, a refrigerating temperature of -40.degree. C. or -80.degree. C. cannot be attained.
Where R-22 is singly used as a refrigerant, a compressor inlet temperature thereof is required to be considerably lowered so as to repress rise of a compressor outlet temperature thereof. However, blending R-142b with R-22 makes it possible to lower the outlet temperature because the outlet temperature of R-142b does not rise so high even if its inlet temperature is comparatively high.
Further, blending R-142b with R-22 forms a nonflammable composition despite the flammability of R-142b thereby improving in safety. FIG. 4 shows flammability relative to mixing ratios of R-142b, R-22, and air, wherein the hatched area is a flammable area while the other area being an nonflammable area. It can be understood from this figure that mixing more than 10 wt % of R-22 can avoid the flammable area of R-142b.
When an ambient temperature is low, for example, less than 0.degree. C. in winter, in case that refrigerant leakage from the refrigerant circuit occurs, and R-22 having a lower boiling point precedently evaporates and dissipates. Therefore, R-142b remains solely or dissolved in the compressor oil. If the refrigerant temperature subsequently is raised due to rise of the ambient temperature, bringing a torch for repairing close to the refrigerant, or the like, only the flammable R-142b flows out, resulting in an eventual explosion thereof.
The present invention aims to overcome the various problems ascribed to the prior art as described above.